The impact of repeated treatment with praziquantel of schistosomiasis in children under six years of age living in an endemic area for Schistosoma haematobium infection

Praziquantel was given every eight weeks for two years to children aged under six years of age, living in a Schistosoma haematobium endemic area. Infection with S. haematobium and haematuria were examined in urine and antibody profiles (IgA, IgE, IgM, IgG1, IgG2, IgG3, and IgG4) against S. haematobium adult worm and egg antigens were determined from sera collected before each treatment. Chemotherapy reduced infection prevalence and mean intensity from 51.8 percent and 110 eggs per 10 ml urine, respectively, before starting re-treatment programme to very low levels thereafter. Praziquantel is not accumulated after periodic administration in children. Immunoglobulin levels change during the course of treatment with a shift towards 'protective' mechanisms. The significant changes noted in some individuals were the drop in 'blocking' IgG2 and IgG4 whereas the 'protecting' IgA and IgG1 levels increased. The antibody profiles in the rest of the children remained generally unchanged throughout the study and no haematuria was observed after the second treatment. The removal of worms before production of large number of eggs, prevented the children from developing morbidity

T cell clones from Schistosoma haematobium infected and exposed individuals lacking distinct cytokine profiles for Th1/Th2 polarisation

T cell clones were derived from peripheral blood mononuclear cells of Schistosoma haematobium infected and uninfected individuals living in an endemic area. The clones were stimulated with S. haematobium worm and egg antigens and purified protein derivative. Attempts were made to classify the T cell clones according to production of the cytokines IL-4, IL-5 and IFN-gamma. All the T cell clones derived were observed to produce cytokines used as markers for the classification of Th1/Th2 subsets. However, the 'signature' cytokines marking each subset were produced at different levels. The classification depended on the dominating cytokine type, which was having either Th0/1 or Th0/2 subsets. The results indicated that no distinct cytokine profiles for polarisation of Th1/Th2 subsets were detected in these S. haematobium infected humans. The balance in the profiles of cytokines marking each subset were related to infection and re-infection status after treatment with praziquantel. In the present study, as judged by the changes in infection status with time, the T cell responses appeared to be less stable and more dynamic, suggesting that small quantitative changes in the balance of the cytokines response could result in either susceptibility or resistant to S. haematobium infection

Schistosomiasis control measures for small irrigation schemes in Zimbabwe

A pilot study was initiated in 1984 on the 600 ha Mushandike Irrigation Project near Masvingo; Zimbabwe; with the objective of developing and field-testing practical guidelines to reduce the risk of schistosomiasis transmission foruse by those involved in planning designing; constructing and operating small-holder irrigation projects in Zimbabwe. Schistosomiasis is a parasitic disease which is particularly prevalent on irrigated land because of high levels of human contact with water and because colonisation by the aquatic snails; which actas its intermediate hosts; is generally favoured by the aquatic environments created within irrigation and drainage systems. A number of important phases of the project are complete. These include formulating citeria for schistosomiasis control; implementing these criteria within the design and construction precesses; establishing regular monitoring of the human and snail populations and introducing micro-computer assisted irringation scheduling to reduce the likelihood of snailcolonisation in parts of the system. [abstract terminated]

Schistosomiasis control measures for small irrigation schemes in Zimbabwe : results from three years of monitoring at Mushandike Irrigation Scheme

A pilot study was initiated in 1984 on the 600 ha Mushandike Irrigation Project near Masvingo; Zimbabwe; with the objective of developing and field-testing practical guidelines to reduce the risk of schistosomiasis transmission for use by those involved in planning; designing; constructing and operating small-holder irrigation projects in Zimbabwe. Schistosomisasis is a parasitic disease which is particularly pravalent on irrigation land because of high levels of human contact with water and because colonisation by the aquatic snails; which act as its intermediate hosts; is generally favoured by the equatic enviornments created within irrigation and drainage systems. A number of important phases of the project are complete. These include formulating criteria for schistosomiasis control; implementing these criteria with the design and construction processes; establishing regular monitoring of the human and snail populations and introducing micro-computer assisted irrigation scheduling to reduce the likelihood of smail colonisation in parts of the system. Interim results form the monitoring exercise are now available which enable comparisons to be drawn between different zones of the project and with irrigated land nearby on which control measures have not been introduced. These results indicate that a combination of concrete lining; irrigation scheduling and using innovative control structures on the infield works has had a major impact on the snail hosts. Some disease transmission is; however; occuring in the pilot areas. This is apparently associated with some unsuitable village lacations; inadequate access to safe domestic water supplies and enhanced flows in some natural drainage channels; This report reviews the monitoring to date and discusses what further studies are needed to establish the effectiveness of the control measures

Schistosomiasis research at the Blair Research Institute - Annual report - 1991

Genetic studies on some schistosome intermediate host snails in Zimbabwe were carried out. The variation in enzyme; electrophoresis patterns and chromosome numbers of snails from different geographical areas were examined. From the data collected and partial analysis of the electrophoresis data; there was no evidence suggesting the existence of more than one species (Balinus globosus) in the studied areas. The chromosome preparations observed did not show any variations in chromosome numbers (n = 18); although eliminating the existence of polyploidy it does not clarify which members of the B. tropicus/truncatus exists in Matabeleland (B. tropicus and/or B. tropicus) hence further research is needed; possibly using Biotechnological techniques

Community based schistosomiasis control in Zimbabwe

The project was established to investigate the feasibility of a national schistosomiasis control programme in Zimbabwe based upon an intergrated approach. The project involved community self help sanitation and water programmes; health education; chemotherapy of school children with praziquantel; and focal mollusciciding. The project was carried out in two rural areas of Zimbabwe with a combined population of over 40;000 people. Madziwa (32;00 people) had all of the above interventions; and Bushu (8.000 people) had only the chemotherapy intervention. Infection with schistosomiasis was determined by the use of reagent strip examination for haematuria. This low cost method of diagnosis was found to be very appropriate and feasible for the examination of large numbers of children and the method was recommended for use in a national control programme. Pretreatment infection levels with schistosomiasis generally exceeded 60in both areas although there was considerable heterogenity in distribution